The first inactivated coronavirus vaccine passes the second phase of trials

  NIH Image Gallery / In the journal, The Lancet published the results of the Phase 1/2 trials antikoronavirusnoy vaccine Corona...


NIH Image Gallery /

In the journal, The Lancet published the results of the Phase 1/2 trials antikoronavirusnoy vaccine CoronaVac from a Chinese company Sinovac. This is the first vaccine based on inactivated viral particles for which the results of the first phases of trials have become known. It appears to have milder side effects than other vaccines. The overwhelming majority of the vaccinated participants have formed neutralizing antibodies to the coronavirus, but how much they really protect against infection will become clear only in the third phase.

When the SARS-CoV-2 vaccine race started, all possible platforms were used to create a vaccine: “killed” and weakened viruses, their individual proteins, and gene fragments, and even vectors based on other viruses (we wrote in the text "On the tip of the needle" ).

So far, mRNA vaccines are leading the race - from companies Pfizer and Moderna, which recently published preliminary results of the third phase of trials and promised 90 and  94.5 percent efficacy, respectively. In second place are adenovirus vaccines: now the third phase is being developed by the Russian Center. Gamalei, as well as AstraZeneca, CanSino, and Johnson & Johnson.

However, there are questions for both technology leaders. The development of mRNA-based vaccines is a new and not yet fully developed method. In this case, a viral gene is introduced into the body so that human cells themselves produce a viral protein and acquaint the immune system with it. But vaccines for other diseases that would act on the same principle do not yet exist, so it is difficult to predict what difficulties may arise with them.

Adenoviral vectors act in a similar way: a viral gene enters the body as part of a neutralized adenovirus, which infects human cells with this gene. This technology is better studied, but it also has its controversial places: for example, it is not clear which adenovirus is better to take, and whether an immune response will arise to it, which will prevent the vaccine from working.

Therefore, other companies continue to develop vaccines using long-established and proven technologies - based on neutralized SARS-CoV-2 particles. The first results of such tests appeared today. This is the inactivated (ie "killed") CoronaVac vaccine from the Chinese company Sinovac Life Sciences.

The vaccine developers presented the results of the combined first and second phase trials. The total was attended by 743 people - the sample comparable to similar studies of British and Chinese adenovirus vaccines and is much higher than the one with which to work, researchers from the Center to them. Gamalei. All volunteers in the CoronaVac trials received two shots, two or four weeks apart. Some received a placebo, others a low dose of the vaccine, and still others a high dose.

According to the results of the first phase (143 people), side effects from vaccination occurred in less than a third of the volunteers (with the exception of one of the groups, where such was 38 percent). All of them were mild (most often limited to pain at the injection site) and disappeared within two days, except for one case when the study participant developed hives, which were removed within three days. This sets CoronaVac apart from other vaccines, which often cause fever in volunteers (we wrote about this in the material "Decomposition into vectors" ).

Frequency and type of vaccination side effects in different groups

Zhang et al. / The Lancet, 2020

Also, in all groups of the first phase of the trial, except for the one that received placebo, antibodies to SARS-CoV-2 (up to 100 percent in different groups) were found in the volunteers, including neutralizing ones - they were the most in the groups with a high dose of the vaccine two weeks after the second injection (up to 83 percent of participants).

Moving to the second phase, the developers changed the strategy for producing the vaccine: they switched from manual cultivation of cells with the virus to growing them in a bioreactor. At the same time, production has become more efficient, and the content of S-protein (to which antibodies are mainly formed) in the vaccine has almost doubled. Therefore, among the participants in the second phase, antibodies to coronavirus were found even more often - up to 100 percent in some groups. And the side effects did not occur more often than in the first phase.

The trial organizers point out several potential weaknesses in their vaccine. For example, their sample did not include people from risk groups (they selected volunteers no older than 59 years), and they also did not track the T-cell immune response after vaccination (which, however, should not change much under the influence of an inactivated vaccine). In addition, the concentration of neutralizing antibodies that were formed in the volunteers was low: their titer ranged from 23.8 to 65.4. This is comparable, for example, with the results Russian adenovirus vaccine (49.3), but much less than in the blood plasma of people who have had COVID-19 - on average, 163.7. However, it is still unknown which titer provides people with protection from infection. The authors of the work also note that in tests on monkeys, CoronaVac successfully protected animals from infection - so, perhaps, such a titer will be enough for people.

Based on their results, Sinovac experts considered that the vaccine was ready for the third phase of trials, which should answer all remaining questions about the effectiveness and protective effect. This phase has already started in Turkey, Indonesia, and Brazil and is expected to involve nearly 30,000 volunteers. In Brazil, trials are now on hold due to the suicide of one of the participants, but it is not yet clear if this is due to the effects of the vaccine.

An inactivated vaccine is also being tested in Russia - the Chumakov Center is working on them. Read about how this vaccine was created in our text "Dead Water". And the rest of the stories about what we know today about coronavirus infection, its symptoms, medications, and vaccines, we have collected in the material.


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Corona Virus Magazine | Healthcare: The first inactivated coronavirus vaccine passes the second phase of trials
The first inactivated coronavirus vaccine passes the second phase of trials
Corona Virus Magazine | Healthcare
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